Planetary sheet slowdown and laydown mechanism

ABSTRACT

A sheet slowdown and stacking mechanism having horizontal grippers for engaging the tail edge of a sheet moving at high speed over a sheet stack followed by release of the leading edge of the sheet from a conveying transport gripper bar, the tail edge of said sheet being carried forward and downward on a curvilinear path engaged by the horizontal grippers which are gyrating about the axis of a rotating reel, said grippers decelerating the forward motion of the sheet substantially to zero at the point of release over the sheet stack for laying down the sheet on the stack pile.

United States Patent Henkel [54] PLANETARY SHEET SLOWDOWN AND LAYDOWN MECHANISM [72] Inventor: Allmen P. Henkel, Lake Forest, Ill.

[73] Assignee: Western Printing Machinery Co.,

Schiller Park, Ill.

22 Filed: March 26,1971

211 Appl.N0.: 128,358

[52] US. Cl ..271/79 [51] Int. Cl. ..B65h 29/28, B65h 29/06 [58] Field of Search ..271/79, 80, 68, 82, 64

[56] References Cited UNITED STATES PATENTS 3,284,081 11/1966 Huck ..271/64 2,093,228 9/1937 Barber ..271/68 2,620,033 12/1952 Wood ..271/68 51 Nov. 21, 1972 FOREIGN PATENTS OR APPLICATIONS 446,462 4/1936 Great Britain ..271/79 Primary Examiner-Richard E. Aegerter Attorney-Charles W. Rummler and William A. Snow [5 7] ABSTRACT A sheet slowdown and stacking mechanism having horizontal grippers for engaging the tail edge of a sheet moving at high speed over a sheet stack followed by release of the leading edge of the sheet from aconveying transport gripper bar, the tail edge of said sheet being carried forward and downward on a curvilinear path engaged by the horizontal grippers which are gyrating about the axis of a rotating reel, said grippers decelerating the forward motion of the sheet substantially to zero at the point of release over the sheet stack for laying down the sheet on the stack pile.

5 Claims, 5 Drawing Figures PATENTED unv 2 1 I972 SHEET 1 BF 4 INVENTOR.

PLANETARY SHEET SLOWDOWN AND LAYDOWN MECHANISM BACKGROUND OF THE INVENTION The present invention relates to non-stop, high speed pile delivery of sheets by positive control of the stacking process permitting more effective sheet stacking at a higher productivity rate than has been achieved in the past.

Machines for automatic sheet deceleration and laydown can be functionally classified as mechanical or vacuum operated. One type of vacuum operated machine employs a power driven slowdown roller in a vacuum box having a slot in its top over which the trailing edge of the sheet is pulled by the transport gripper bar. The peripheral speed of the roller against which the sheet is pulled by the vacuum is less than the speed of the sheet so that the traveling sheet is slowed down by the contact. Air blast from above the sheet can assist vacuum pull to make the contact more positive. Although not positive in control, this slowdown means is widely used on printing presses although it cannot be used to deliver sheets with die cut or perforate holes or cutouts.

One purpose of automatic sheet slowdown devices is to obviate the buckling of the forward moving sheet material as the front edge is brought to rest against the stop plate in its deposition on the stack pile and to achieve orderly piling of sheets at as high a speed as is practical.

Another purpose is to move the sheets as quickly as possible downward with a minimum of dependence on gravity to settle the sheet to rest in the desired position on top of the pile before the arrival of the next sheet. This factor is of increasing importance as higher sheet speeds are sought.

Completely controlled slowdown of sheets from the tail where the tail edge of the sheet is engaged by gripper pads which are in a deceleration portion of a path of simple harmonic motion is a most effective method of sheet slowdown. Inertia of the sheet is used to advantage to maintain the sheet planar in its bodily motion along a curvilinear path from pick-up to deposition on the pile. Only the inertia slowdown avoids the buckling problems of high speed sheet skidding to a stop on top of the pile.

It has been said that the speed of a rotary press is determined primarily by the sheet delivery system. Thus, with efiective tail edge control of the sheet, the

' speed of the press can be increased and the reliability of the press operation benefited.

The U.S. Pat. to Ellis et al., No. 3,378,256, relates to a sheet slowdown mechanism which includes a vacuum cup gripper which is moved in a substantially horizontal position along an elongated endless path, which vacuum cup grips a sheet while moving at sheet speed and then decelerates to slow the speed of the sheet, where movement of the sucker member through its endless path is effected by an actuating means including a pair of rotatable drive elements connected with the vacuum cup by a parallel four-bar linkage arrangement wherein the actuating means also includes a separate actuating mechanism, for imparting superim posed horizontal and vertical movement to the vacuum cup, comprised of a link member pivotally connected with the vacuum cup member and driven by a rotatable drive element. This slowdown mechanism suffers from the disadvantage that the vacuum cup member, after it takes the sheets, tilts relative to the horizontal to clear the pile in its endless path causing'some problemsin sheet bending which prohibits its application to the slowdown of die-cut sheets.

The U.S. Pat. to Huck, No. 3,284,081, is closest to the concept of a gyrating gripper for sheet piling. FIGS. 8, 9 and 10 of that patent show an arrangement whereby the leading edge of a sheet delivered from the press is engaged by a gripper mounted on the periphery of a rotary transfer member. In that case, however, the sheet is not released until the rotary member has traveled substantially through of revolution. Thus the sheet deposited on the pile is inverted, printed side down, and the sheet is moving at maximum speed at the time of release. This patent cannot be considered to suggest the idea of sheet slowdown by a constant level gyrating gripper releasing at the point of zero forward movement along a path of harmonic motion.

Spooner et al. U.S. Pat. No. 3,081,082 discloses another arrangement of vacuum means for engaging a printed sheet subsequent to its release from the delivery chain. The disclosure of this patent includes an air blast arrangement for slowing the forward progress of the sheet as it is delivered to the pile. The patent does not suggest the invention of the constant level gyrating gripper.

Yingling et al. U.S. Pat. No. 2,942,878 provides a sheet slowdown mechanism having vacuum cups engagable with the tail of the sheets to deposit them on the pile, said slowdown mechanism being operated by an over-center rotary link drive for moving the vacuum cups in a continuous decelerating forward and downward path from sheet pick-up to release. This slowdown mechanism, which operates to accelerate the vacuum cup member to initially engage and take the sheet while moving at sheet speed, suffers from the disadvantages that it is complex and the vacuum cup member, after it takes the sheet, tilts relative to the horizontal causing some problems in sheet ending and sheet peeling off the vacuum cup member.

U.S. "Pat. No. 2,093,228 is an invention directed to improvements in flat sheet deliveries for web printing .presses and more particularly to means for operating sheet tail end engaging devices whereby they are moved in an endless path and operated to successively grasp the tail end of a sheet, stop its travel and depress it below the path of its endless delivery carrier and then to release the tail end of the sheet after its supporting surface on the delivery carrier has moved out from under it, thereby permitting the sheet to drop on the pile. This patent differs from the present invention in that the forward descending movement of the constant level gripper is achieved by complex cam action rather than simple planetary gear means.

Positive deceleration from the tail edge of a sheet moving at high speed is the optimum means of control for rapid piling of successive sheets. There is a need, therefore, for a simple sheet laydown device which delivers the sheet without damage against the stop plate of the pile and with decreased time interval between successive sheets by engaging the tail edge of the rapidly moving sheet so as to keep constantly horizontal and to decelerate it under positive control, without bending the sheet, along a curvilinear downward path to a point of release close to the top of the pile.

SUMMARY OF THE INVENTION The gist of this invention lies in the adaption of a gripper reel having one or more sheet tail edge grippers which are maintained in a generally horizontal position while gyrating about the reel axis by means of suitable planetary gearing so that the grippers at the top of their gyration will engage the tail edge of a sheet carried by a transport gripper bar while traveling at the speed of the transport bar. As the grippers continue through the next 90 of their gyration about the reel axis carrying the sheet, the leading edge of the sheet having been released from the transport gripper bar shortly after engagement of the tail edge of the sheet by the reel carried gripper, the forward speed of the grippers and the sheet decreases, harmonically, to almost zero, where the grippers automatically release the tail edge of the sheet for laydown of the sheet between the guides of the stack pile. This arrangement achieves the purpose of stopping of forward travel of the sheet in such a manner that the sheet tail is carried downwardly and released close to the top of the pile without bending and the front edge is subsequently brought to rest without damage against the pile stop plate.

Accordingly, the principal object of this invention is to provide a sheet slowdown mechanism comprising a gyrating gripper having timed cam actuated engagement of the tail edge of a forward moving sheet while at the top of its gyration and providing positively controlled forward deceleration of the sheet while in a forward and downward curvilinear path, followed by a cam actuated release at the position when the forward movement of the gripper and sheet is approximately zero and the sheet can be dropped directly onto the stack pile, the gyrating gripper being maintained in a substantially horizontal position at all times.

DESCRIPTION OF THE DRAWINGS A specific embodiment of this invention is shown in the accompanying drawings, in which;

FIG. 1 is a fragmentary side view of the sheet deceleration and laydown mechanism of this invention along section line l] of FIG. 2 showing the moving sheet released by the tail edge gripper for laydown on the stack;

FIG. 2 is a fragmentary top plan view of the sheet deceleration and laydown mechanism of this invention;

FIG. 3 is a fragmentary side view of the sheet deceleration and laydown mechanism of this invention, as taken along section lines 3-3 of FIGS. 2 and 4, in the sheet pickup position showing the gyrating horizontal sheet-tail-edge grippers and the mechanism for operating them;

FIG. 4 is a fragmentary end view of the sheet deceleration and laydown mechanism of this invention along section line 44 of FIG. 2 in the sheet pickup position showing the gyrating tail edge grippers mounted on the tail edge gripper bar, the horizontal position of which is controlled by a planet gear system; and

FIG. 5 is a schematic showing a time-picture sequence of operation of the sheet deceleration and laydown mechanism, showing the approach phase A of the tail edge grippers relative to the tail edge of the sheet, the pickup phase B with closure of the grippers on the tail edge of the sheet, the disengagement of the sheet delivery transport grippers from the leading edge of the sheet at sheet phase C, and the release of the tail edge grippers from the tail edge of the sheet at stack phase D. 1

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to FIGS. 1 and 2, which show fragmentary sections of the frame 10 of a rotary, sheet fed printing, die cutting and creasing press or other high speed converting machine comprising in part the controlled laydown and stacking of sheets of paper, solid paperboard, corrugated paperboard, metal or other sheet materials by the deceleration and laydown mechanism 11 of this invention, it. will be seen that a sheet 12 is drawn at high speed from the converting equipment by a more-or-less conventional sheet delivery means transport gripper bar 13' which is mounted on chain conveyor 14 and which has a plurality of transport grippers 15' engaging the leading edge 16' of the sheet 12. The transport grippers 15 have upper gripper pads 17, which engage the leading edge 16 of sheet 12 as it is delivered from the rotary sheet converting mechanism, and are mounted on the preceding transport gripper bar 13. The transport gripper bar 13 carries a rotatable gripper shaft 21 journaled on the bar 13 and having a lever arm 20, extending radially therefrom, for carrying a cam follower 18 which engages and runs along a linear cam track 19. The gripper shaft 21 carries a plurality of lower gripper pads 17', one opposite each upper gripper pad 17 for coaction therewith, and these lower gripper pads are actuated to close on the leading edge of sheet 12 by rotation of the gripper shaft 21 as the cam follower 18 moves onto and off from the cam track 19. The cam track 19 is mounted on the framelO and extends along the path of the cam follower 18, as it travels with the transport gripper bar 13, and its position along the said path determines the point of engagement and the point of disengagement of a sheet 12 delivered from the rotary press or the like mechanism.

Referring again to FIG. 1, sheet 12' is engaged between a plurality of upper tension reels 23 and a plurality of lower sheet delivery control reels 24, the con- I trol reels 24 being part of a lower sheet delivery control reel assembly 25 which is rotatably mounted on a driven shaft 26 journaled on the frame 10. As shown in FIGS. 1 and 2, each reel 24 is provided with a plurality of sheet tail edge grippers 27 mounted on a gripper bar 28.

Referring to FIG. 3, sheet tail edge gripper bar 28 carries a rotatable gripper pad support shaft 32 journaled on the bar 28 and having a cam lever 39 extending radially therefrom, for carrying a cam follower 33 which engages the running surface 34 of a circumferential cam 35. The gripper shaft 32 carries a plurality of upper gripper pads 29, one opposite each of the lower gripper pads 29' for coaction therewith, and these upper gripper pads are actuated to close on the tail edge of sheet 12' by rotation of gripper shaft 32 as the cam follower 33 engages the running surface 34 of circumferen-tial cam 35. Referring to FIG. 4, it will be seen that the cam 35 is fixedly mounted on and constrained to rotate with the reel end support arm 36 so that the cam follower 33 and its position along said running surface 34 of the cam 35 determines the point of pickup and release of a sheet 12' by the horizontal grippers 27 of sheet deceleration and laydown mechanism 11.

Sheet tail edge gripper bar 28 and grippers 27 are maintained horizontal by the action of deceleration and laydown mechanism 11 in their gyration about an endless circular path. As shown, the deceleration and laydown mechanism 11 is comprised of the planetary gear assembly 31 shown in FIG. 4, in addition to the sheet tail edge grippers 27 discussed above. The gear assembly 31 is rotatably mounted on a reel end support arm 36 which is rotatably mounted on drive shaft 26 journaled in frame 10. The reel end support arm 36 has an outer end 36a, an inner side 36 and an outer side 36", with support bar 30 mounted to the opposite outer end 36b of the reel support arm 36 for supporting the plurality of reels 24 intermedially spaced therebetween. The reel end support arm 36 carries a spindle 37 fixedly mounted to its outer end 36a and to its inner side 36', respectively, and a gripper planet gear 38, shown in FIG. 3, is rotatably mounted on the spindle 37 which fixedly carries the end of the gripper bar 28 rigidly mounted thereto. The gripper 27 mounted on the gripper bar 28 then rotates about the spindle 37 as the spindle 37 gyrates about the drive shaft 26.

The reel end support arm 36 pivotally carries the primary idler planet gear 42, shown in FIG. 4, fixedly mounted on an idler shaft 43, disposed adjacent the inner side 36' of the support arm 36, and which is enmeshed with a gripper planet gear 38. The idler shaft 43 lies between the spindle 31 and drive shaft 26. Again, as shown in FIG. 4, the idler shaft 43 is rotatably supported by and extends through the end support arm 36 and fixedly mounts a secondary idler planet gear 42' adjacent the outer side 36" of arm 36. The idler planet gears 42 and 42' have the same pitch diameter, and the sun gear 44, which is fixedly mounted to frame coaxial with drive shaft 26, has the same pitch diameter as said gripper planet gear 38 and meshes with the secondary idler planet gear 42', as shown in FIGS. 3 and 4, so that in the gyration of the primary and secondary planet gears 42 and 42' and the gripper planet gear 38 about sun gear 44, the gripper planet gear 38 rotates the same number of turns in the revere direction as the reel end support arm 36, on the drive shaft 26, rotates in the forward direction with the net result that the gripper planet gear 38 does not rotate but maintains a fixed or set angular position in space regardless of the angular position of reel end support arm 36. Once the sheet tail edge gripper 27 is set horizontal for sheet deceleration and laydown control, the sheet tail edge gripper bar 28, affixed to planet gear 38, maintains the sheet tail edge grippers 27 horizontal, regardless of the angle of reel end support arm 36. Tail edge 22 of sheet 12', which is held in the grip of gripper 27, is then also maintained horizontal and sheet 12', which has previously been disengaged from transport grippers 15, as shown in FIG. 5, is under the control of tail edge gripper 27 and thus remains essentially horizontal throughout its forward and downward curvilinear path in the course of its deceleration and laydown. Once sheet 12 is released for laydown on stack 41, it is a free body with essentially downward and very little forward movement. Stop plate 20 and side guides 19 and 19' mounted adjacent the end and sides of the stack 41, respectively, ensure that the sheet 12 falls onto the stack 41 without slipping or buckling. Back stop 20' prevents back fall of the sheet 12 as it drops down onto the stack 41.

In the description of this sheet slowdown invention, only those elements shown in the drawings are designated by numerical reference numbers in the specification and drawings. Elements on the side opposite in exact contra distinction thereto will be named by implication.

In the operation of the sheet deceleration and laydown mechanism of this invention, the time-picture sequence as shown in FIG. 5 has been broken into sheet tail edge approach phase A, sheet pickup operation B, sheet deceleration phase C and sheet release and stacking phase D.

FIG. 5 shows approach phase A wherein the decelerating mechanism 11 is moving to pickup of sheet 12" during the course of which the tail edge gripper 27, mounted on tail edge gripper bar 28, approaches the tail edge 22 of sheet 12' from below and behind along a path of gyration about the axis of the driven shaft 26. The movable upper gripper pad 29 of tail edge gripper 27 is opened from the fixed level lower gripper pad 29' during this approach. The approach of the tail edge grippers 27 is coordinated with the transport of the tail end 22 of sheet 12 so that the horizontal lower gripper pad 29' moves up under tail end22' of sheet 12' in its approach to the top or 12 o'clock position of the delivery control reel 24 for sheet pickup operation B.

The sheet pickup operation B, shown in FIGS. ,3 and 5, occurs at the top of the gyrating path of the grip pers 27, during their rotation about the driven shaft 26, when the movable upper gripper pad 29 closes down on the tail end 22 of the sheet 12 as it lies on the horizontal fixed lower gripper pad 29' underneath. For proper pickup, the circumferential speed of the gripper 27 about driven shaft 26 must be substantially the speed of the sheet delivery conveyor chain 14. At the instant of pickup, the leading edge 16' of sheet 12 is still engaged by transport grippers 15 and remains thus for a relatively short time thereafter. After pickup and subsequent disengagement by transport grippers 15, the sheet 12' is under the control of the deceleration and laydown mechanism 11 which acts to maintain the sheet 12 substantially horizontal.

In sheet pickup operation B, the closing of movable upper tail edge gripper pad 29 on the end 22 of sheet 12', the gripper bar 28 and lower gripper pad 29' are maintained at a constant level in a substantially horizontal position by the gyration of the grippers 27 about drive shaft 26 under the action of the planetary gear assembly 31. The upper gripper pads 29 are mounted on an upper gripper pad support shaft 32 which is cammed to open and close the upper gripper pads 29 on the end of sheet 12' in the proper time sequence for pickup and release of the sheet.

Reference again to FIG. 5 also shows that the grippers 27, in their horizontal position gyration throughout their endless circular path, increase the radius of their circular path after the pickup operation and throughout the downward curvilinear path of phase C. This articulating motion of the grippers 27 allows the transport grippers to hold to leading edge 16 of sheet 12 a little longer than do conventional pile deliveries employing vacuum drums or other vacuum means and thus helps to maintain the horizontal stability of the sheet 12 during laydown on the stack. This is especially important in the case of jogging or slow run compared to fast run as the tail end grippers 27 positively convey the end of the sheet 12 down and away from the path of the next oncoming transport gripper bar 13' and engaged sheet 12'.

At the instant in its forward and downward curvilinear path at which forward movement has substantially decelerated to zero, the sheet 12 is released by horizontal gripper 27. This corresponds to release operation D after which sheet 12 is delivered downwardly as a free body onto the pile 41.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that the details of construction shown may be altered or omitted without departing from the spirit of the invention as defined in the appended claims.

lclaim:

1. A mechanism for the horizontal slowdown and laydown deceleratingly along a forwardly and downwardly curvilinear path of a sheet delivered from a rotary printing, die cutting or other high speed converting means, having a frame, a sheet delivery transport gripper means mounted for movement on said frame, and a drive shaft horizontally joumaled therein, comprising:

a. a pair of laterally spaced end support arms mounted on said drive shaft for rotation about its axis,

. a planetary gear means mounted on each of said support arms,

c. a sheet tail end gripper means mounted on and extending between said planetary gear means for opera-tion thereby to pick up the tail edge of said sheet, maintain it horizontal in its forward and downward movement along said curvilinear path, and release it at the extent of its forward travel, and

d. a cam means for closing and opening said tail end gripper means, in the pickup and release of said trailing edge of said sheet, in the proper time sequence with the delivery of the sheet from said converting means.

2. A horizontal slowdown and laydown mechanism according to claim 1 wherein the planetary gear means for maintaining the sheet horizontal comprises:

a. a sun gear fixed to the frame at each support arm coaxially with the drive shaft,

b. a gripper gear rotatably mounted on a spindle carried by each support arm at its outer end, and

c. an idler gear means rotatably mounted on each support arm and enmeshed with said sun gear and said gripper gear.

3. A sheet horizontal slowdown and laydown mechanism according to claim 2 wherein the sheet tail ed e ri er means com rises:

2%. g gi' ipperbar mouriied on said grippergears and fixedly mounting a plurality of horizontal laterally spaced lower gripper pads, and

b. a gripper shaft rotatably mounted on said gripper gears and carrying a plurality of laterally spaced movable upper gripper pads, one opposite each fixed lower gripper pad, for coaction therewith in the. pickup and release of the tail edge of said sheet therebetween.

4. A sheet horizontal slowdown and laydown mechanism according to claim 3 wherein the cam means for actuating the sheet tail edge gripper means in pickup and release of said trailing edge of said sheet comprises:

a. a circumferential cam fixedly mounted on the end support arm centered on the spindle mounted to each support arm, and

b. a cam follower in running engagement with said cam mounted on a lever arm radially extending from said gripper shaft to open and close the movable upper gripper pad on the tail edge of the sheet lying on the fixed horizontal gripper pad for pickup and release of the sheet in the proper time sequence with delivery of the sheet from the converting means.

5. A sheet horizontal slowdown and laydown mechanism as set forth in claim 2 wherein the idler gear means comprises two gear sets each set having a common shaft journaled in each end support arm and each set having a gear on each side of each end support arm. 

1. A mechanism for the horizontal slowdown and laydown deceleratingly along a forwardly and downwardly curvilinear path of a sheet delivered from a rotary printing, die cutting or other high speed converting means, having a frame, a sheet delivery transport gripper means mounted for movement on said frame, and a drive shaft horizontally journaled therein, comprising: a. a pair of laterally spaced end support arms mounted on said drive shaft for rotation about its axis, b. a planetary gear means mounted on each of said support arms, c. a sheet tail end gripper means mounted on and extending between said planetary gear means for opera-tion thereby to pick up the tail edge of said sheet, maintain it horizontal in its forward and downward movement along said curvilinear path, and release it at the extent of its forward travel, and d. a cam means for closing and opening said tail end gripper means, in the pickup and release of said trailing edge of said sheet, in the proper time sequence with the delivery of the sheet from said converting means.
 1. A mechanism for the horizontal slowdown and laydown deceleratingly along a forwardly and downwardly curvilinear path of a sheet delivered from a rotary printing, die cutting or other high speed converting means, having a frame, a sheet delivery transport gripper means mounted for movement on said frame, and a drive shaft horizontally journaled therein, comprising: a. a pair of laterally spaced end support arms mounted on said drive shaft for rotation about its axis, b. a planetary gear means mounted on each of said support arms, c. a sheet tail end gripper means mounted on and extending between said planetary gear means for opera-tion thereby to pick up the tail edge of said sheet, maintain it horizontal in its forward and downward movement along said curvilinear path, and release it at the extent of its forward travel, and d. a cam means for closing and opening said tail end gripper means, in the pickup and release of said trailing edge of said sheet, in the proper time sequence with the delivery of the sheet from said converting means.
 2. A horizontal slowdown and laydown mechanism according to claim 1 wherein the planetary gear means for maintaining the sheet horizontal comprises: a. a sun gear fixed to the frame at each support arm coaxially with the drive shaft, b. a gripper gear rotatably mounted on a spindle carried by each support arm at its outer end, and c. an idler gear means rotatably mounted on each support arm and enmeshed with said sun gear and said gripper gear.
 3. A sheet horizontal slowdown and laydown mechanism according to claim 2 whereIn the sheet tail edge gripper means comprises: a. a gripper bar mounted on said gripper gears and fixedly mounting a plurality of horizontal laterally spaced lower gripper pads, and b. a gripper shaft rotatably mounted on said gripper gears and carrying a plurality of laterally spaced movable upper gripper pads, one opposite each fixed lower gripper pad, for coaction therewith in the pickup and release of the tail edge of said sheet therebetween.
 4. A sheet horizontal slowdown and laydown mechanism according to claim 3 wherein the cam means for actuating the sheet tail edge gripper means in pickup and release of said trailing edge of said sheet comprises: a. a circumferential cam fixedly mounted on the end support arm centered on the spindle mounted to each support arm, and b. a cam follower in running engagement with said cam mounted on a lever arm radially extending from said gripper shaft to open and close the movable upper gripper pad on the tail edge of the sheet lying on the fixed horizontal gripper pad for pickup and release of the sheet in the proper time sequence with delivery of the sheet from the converting means. 